JP2000256794A - High toughness high damping alloy and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high damping alloy for a low Cr structural material in which damping properties and strength-toughness are reconciled. SOLUTION: In steel having a compsn. contg., by weight, <=0.03% C, 0.01 to 3.5% Si, 0.3 to 3.0% Mn, <=0.02% P, <=0.010% S, 0.01 to 5.0% Cr, 0.002 to 3.5% Al and <=0.01% N, if required, added with one or >= two kinds among Cu, Ni, Mo, W, Nb, Ta, V, Ti, Zr, B, Ca, Mg and rare earth metals in suitable ranges, and consisting of the balance Fe with inevitable impurities, as to the surface and back faces of the steel sheet, respectively, the average ferrite grain size to 1/6 sheet thickness in the sheet thickness from the surface is controlled to 70 to <150 μm, the average ferrite grain size at the inside of the steel sheet other than the regions is controlled to 20 to <50 μm, also, the (200) plane intensity ratio of the ferrite phase by X-ray diffraction measured at the part of 1/8 sheet thickness in the sheet thickness direction from the surface is controlled to >=1.5, and the (200) plane intensity ratio by X-ray diffraction measured at the center part of the sheet thickness is controlled to >=3.0, by which its damping properties and toughness are reconciled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration damping alloy having both strength and toughness which can be used as a structural material for ships, bridges, industrial machines, buildings, and the like, and a method for producing the same.

[0002]

2. Description of the Related Art Recently, there has been an increasing demand for quietness and vibration suppression for ships, bridges, industrial machines, and buildings. As one of the measures, high damping properties are required for structural materials. Are increasing. That is, for example, noise and vibration during high-speed railway running on a bridge or large-scale civil engineering, construction work is to be suppressed by the vibration damping effect of the structural material itself, and the structural material for this purpose is, Strength, toughness,
It is necessary to have both basic properties necessary for a structural material such as workability and weldability and vibration damping properties.

In order to satisfy the above characteristics, a resin sandwich type vibration damping steel plate which has been generally used in the past is insufficient. That is, the weldability and bending workability of the resin sandwich type vibration damping steel sheet are inferior to those of general steel materials, and their use is limited.

[0004] As a metal material which can replace the resin sandwich type vibration damping steel sheet, particularly an iron-based material which is advantageous as a structural material in terms of weldability and cost, hysteresis due to irreversible motion of domain wall movement under the action of alternating stress due to vibration. A typical example is a ferromagnetic damping alloy using a mechanism that exhibits damping properties. For this purpose, a ferrite single phase structure is advantageous, and therefore, a ferrite stabilizing element is added. Specifically, examples of materials to which Al and Si are added and materials to which Cr is added are disclosed. An example of the former is a ferromagnetic damping alloy containing up to 7.05% of Al and up to 4.5% of Si, as shown in JP-A-4-99148. Is described in JP-A-52-7
As shown in Japanese Patent No. 3118, a ferromagnetic damping alloy containing 8 to 30% of Cr or a relatively small amount of Cr of 1 to 5% as disclosed in Japanese Patent Application Laid-Open No. 6-22058. There is a ferromagnetic damping alloy.

However, these ferromagnetic damping alloys contain a large amount of ferrite stabilizing elements such as Al, Si, and Cr, and have a coarse phase because they do not undergo transformation in a ferrite single phase. Also, even when transformation occurs, it is difficult to achieve the toughness required as a structural material because it is necessary to increase the crystal grain size in order to secure damping properties.

As a method of improving the vibration damping property without impairing the toughness, a technique of optimizing the texture by devising tempering or annealing conditions is disclosed in, for example, Japanese Patent Application Laid-Open No. 10-72643.
However, it is difficult to further improve the toughness and the vibration damping property by only adjusting the tempering conditions and the annealing conditions.

[0007]

SUMMARY OF THE INVENTION In the present invention, the amount of Cr is 5
It is an object of the present invention to provide a low-alloy ferromagnetic type damping alloy exhibiting austenite / ferrite transformation of about% or less and having both good toughness and good damping property, and a method for producing the alloy.

[0008]

Means for Solving the Problems The crystal grain size, dislocation density, solute C, N,
In addition to precipitates, texture has a significant effect
As disclosed in Japanese Patent Application Laid-Open No. H10-72643, the present inventors have found that dislocation density is almost identical under tempering or annealing conditions, solid solution C and N, and precipitate amount are almost identical under chemical composition, tempering and annealing conditions. Is determined, it is important to control the crystal grain size and texture to further improve the toughness and damping properties. The effects of diameter and texture were studied in detail.

As a result, the influence of the crystal grain size and the texture on the vibration damping properties is different between the surface and the inside of the material, and the coarse grains and the (100) aggregate have a certain thickness in the surface layer on the front and back surfaces. It has been found that, if the structure is developed, the vibration damping property can be maintained well even if the internal particle size is relatively fine. Regarding toughness, even if the surface layer is coarse,
Since the toughness of the material as a whole is not impaired if the portion where the internal stress is high in the triaxiality is fine grains, any material having a different crystal grain size and texture between the surface layer and the inside as described above can be used. If this is the case, it is possible to achieve both excellent toughness and vibration damping properties more than before.

[0010] The present inventors have also proposed means for separately producing different crystal grain sizes and textures in the surface layer and the inside. That is, by devising the hot rolling, by introducing an appropriate processing strain only to the surface layer portion, when subjected to an appropriate heat treatment after rolling, the crystal grain and texture different from each other in the surface layer and inside. Can be made separately.

The inventors have reached the present invention based on the above-mentioned new findings, and the gist is as follows.

(1) Each of the front and rear surfaces of the steel sheet has an average ferrite grain size of 7 from the front surface to 1/6 of the sheet thickness in the thickness direction.
0 μm or more and less than 150 μm, the average ferrite grain size inside the steel sheet other than the above area is 20 μm or more and less than 50 μm, and ferrite by X-ray diffraction measured at a portion of 1/8 of the thickness in the thickness direction from the surface. The high toughness control wherein the (200) plane intensity ratio of the phase is 1.5 or more, and the (200) plane intensity ratio of the ferrite phase measured by X-ray diffraction at the center of the plate thickness is 3.0 or more. Vibration alloy.

(2) C: 0.03% or less, Si: 0.01 to 3.5%, Mn: 0.3 to 3.0% by weight.
%, P: 0.020% or less, S: 0.010% or less, Cr: 0.01 to 5.0%, Al: 0.002 to
3.5%, N: 0.01% or less, the balance being Fe
And (1) characterized by comprising unavoidable impurities.
High toughness vibration damping alloy described in 1.

(3) Cu: 0.05-1.
5%, Ni: 0.05 to 2.0%, Mo: 0.05 to
2.0%, W: 0.05 to 2.0%, Nb: 0.00
5 to 0.2%, Ta: 0.005 to 0.5%, V:
0.005 to 0.5%, Ti: 0.002 to 0.02
%, Zr: 0.002 to 0.10%, B: 0.000
The high toughness damping alloy according to the above (2), further comprising one to two or more of 3 to 0.003%.

(4) Ca: 0.001% by weight
0.05%, Mg: 0.0002-0.01%, RE
M: one or more of 0.001 to 0.05% of the above (2) or (3).
High toughness vibration damping alloy described in 1.

(5) The steel slab is heated to 1000 ° C. or higher and 1300
Immediately after heating to below ℃ or above 950 ℃
Rough rolling with a cumulative draft of 80% or less in the tenite range
10% of the billet thickness just before starting the following steps
The surface area corresponding to ~ 35% is A_r3Temperature above the transformation point
Starting cooling at a cooling rate of 2 to 40 ° C./s from _r3Strange
Stop cooling at less than the state and return to heat at least once
In the process of reheating after the last cooling
In the meantime, finish rolling with cumulative reduction of 10 to 80% is completed.
After that, the heating temperature is further increased from 650 ° C. to A_C1Tempering of transformation point
Or performing an annealing treatment.
(1) Production of the high toughness vibration damping alloy according to any one of (1) to (4)
Construction method.

(6) The steel slab is heated at a temperature of 1000 ° C. or more to 1300
After the rough rolling at a cumulative rolling reduction of 10% to 80% to complete the rolling at 900 ° C or lower, the starting temperature is lower than the _Ar3 transformation point, the ending temperature is 600 ° C or higher, and one pass is performed. The rolling reduction per unit is 20% or less and the cumulative rolling reduction is 30
High-toughness according to any one of the above (1) to (4), wherein a finish rolling of up to 80% is carried out, and thereafter, a tempering or annealing treatment at a heating temperature of 650 ° C. to A _C1 transformation point is performed. Manufacturing method of damping alloy.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The damping property of a ferromagnetic type damping alloy is expressed by energy loss at the time of moving a domain wall when an external force is applied. This is a necessary condition for improving the performance. Therefore, in order to increase the crystal grain size of the conventional ferromagnetic damping alloy, a large amount of a ferrite stabilizing element is added to eliminate the austenite / ferrite transformation to form a ferrite single phase without transformation or a high temperature ferrite. It has been common practice to make the crystal grains coarse by devising a manufacturing method such as tempering.

However, since increasing the crystal grain size leads to deterioration of toughness on the other hand, it is inherently difficult to secure toughness in a ferrite single-phase alloy without transformation because of its extremely large crystal grain size. there were. On the other hand, in the case of having an austenite / ferrite transformation such as a low Cr ferromagnetic type vibration damping alloy, the crystal grain size can be controlled to some extent by heat treatment, but, contrary to the ferrite single phase alloy, the grain size is reduced. It was more difficult to perform tempering or annealing at a high temperature near the A _C1 transformation point for coarsening.

In the case of controlling the crystal grain size by high-temperature tempering in a low Cr-based damping alloy, it is not always easy to secure a necessary degree of toughness as a structural material while improving the damping property. That is, if the tempering temperature is too low, the particles are not sufficiently coarsened and the vibration damping properties are inferior.On the contrary, if the tempering temperature is too high and the temperature of the two-phase region is slightly increased, reverse transformed austenite is formed and finally martensite to Transformation into agglomerates of bainite or carbides, the structure deteriorates toughness, and at the same time, strain is introduced during transformation from austenite to the structure, so that the vibration damping property also deteriorates. Even if the tempering temperature is appropriate, a mixed grain structure may be exhibited depending on the manufacturing history before tempering.

As means for improving the vibration-damping properties of fine grains,
As shown in JP-A-10-72643,
In order to develop the <100> orientation, which is the easy magnetization orientation of ferrite, there is a method of developing a (100) texture parallel to the steel sheet surface.

The present inventors have investigated in detail the effects of the crystal grain size and the (100) texture on the vibration damping property and toughness,
"Each of the front and back sides of the steel sheet has a thickness of 1
The average ferrite grain size up to / 6 is 70 μm or more and 150
The average ferrite grain size inside the steel sheet other than the above-mentioned region is 20 μm or more and less than 50 μm, and the ferrite phase by X-ray diffraction measured at a portion having a thickness of 1/8 in the thickness direction from the surface ( 200) When the surface strength ratio is 1.5 or more,
By ensuring that the (200) plane intensity ratio of the ferrite phase measured by X-ray diffraction at the center of the sheet thickness is 3.0 or more, it is possible to achieve both toughness and vibration damping properties that are superior to those of the related art. I found that.

From the mechanism of the vibration damping property, the contribution of the steel sheet structure factor to the vibration damping property is not uniform at the steel sheet part, and the contribution near the steel sheet surface is large. On the other hand, regarding toughness,
In many cases, the inner part having a higher stress triaxiality is more problematic. That is, if it is possible to control the structure and the material in consideration of the damping property on the surface layer and the toughness inside, it is possible to achieve both the damping property and the toughness, which are usually difficult to achieve.

In order to secure vibration damping properties, it is necessary to limit the texture defined by the ferrite grain size and the surface strength ratio.
In order to ensure toughness, it is necessary to reduce the ferrite grain size particularly near the center of the thickness to a certain value or less. In other words, each of the front and rear surfaces of the steel sheet is 1/6 of the thickness in the thickness direction from the front surface
Average ferrite particle size up to 70μm, 150μm
It is necessary that the average ferrite grain size inside the steel sheet other than the above region is not less than 20 μm and less than 50 μm. The structure of the surface layer plays a major contribution to the damping properties, and in order to optimize the grain size in this region with respect to the damping properties, the average ferrite grain size needs to be in the range of 70 μm or more and less than 150 μm. It is. Generally, it is thought that the larger the ferrite grain size becomes, the better the vibration damping property becomes.However, according to the experimental results of the present inventors, there is an optimum ferrite grain size, However, the damping properties are saturated or rather deteriorate. In other words, the lower limit of the ferrite grain size is required to be 70 μm or more in the surface layer portion from the surface to the thickness in the thickness direction up to 1/6 of the thickness. Is not sufficient, and it is necessary that the thickness be less than 150 μm.
This is because the effect of improving the vibration damping property is saturated or rather deteriorated with coarse grains of m or more, and the toughness is adversely affected even in the surface layer.

On the other hand, the area other than the surface layer from the surface up to 1/6 of the sheet thickness in the sheet thickness direction has a small degree of influence on the vibration damping properties of the steel sheet, but is not necessarily completely free of the influence. It is necessary to define the ferrite grain size. That is,
The average ferrite grain size inside the steel sheet other than the surface layer up to 1/6 of the thickness in the thickness direction from the surface is 20 μm or more and 50 μm
Must be limited to less than This means that the ferrite grain size is reduced by 2 even in the steel sheet inner region, which has a small effect on the vibration damping property.
If the thickness is not more than 0 μm, even if the structural factor in the surface layer region satisfies the present invention, the damping property of the steel sheet is not sufficiently improved. On the other hand, the upper limit is limited to less than 50 μm for the purpose of securing toughness. This is because sufficient toughness as a structural material cannot be ensured unless the grain size is reduced to less than 50 μm.

The above is the reason why the grain size is limited among the structural requirements of the present invention. In order to achieve both vibration damping property and toughness, it is necessary to further control the texture. In other words, to ensure toughness, it is necessary to make the grains relatively fine. On top of that, in order to improve the damping properties, the easy magnetization orientation of the ferrite phase is parallel to the steel sheet surface. It is preferable to integrate certain (100) orientations.
Also in this texture, the influence on the vibration damping property is stronger in the surface layer portion and becomes weaker as it goes inside the steel sheet. Therefore, it is preferable to develop the texture on the surface of the steel sheet. However, when the texture is developed by ordinary rolling or rolling and heat treatment, the degree of development of the texture in the surface layer is small.

The present inventors set forth in claim 5 or 6 of the present invention.
The steel plates with various texture distributions, including the texture distribution obtained by normal hot rolling, are manufactured by the methods and various methods described in (1), and the effect of texture on the damping properties and material properties is examined. As a result, with the crystal grain size being within the limited range of the present invention, "the (200) plane intensity ratio of the ferrite phase by X-ray diffraction measured at a site of 1/8 in the thickness direction from the steel sheet surface was 1%. 0.5 or more, and the (200) plane intensity ratio of the ferrite phase determined by X-ray diffraction measured at the center of the sheet thickness is 3.0 or more ”,
By doing so, it has been found that the vibration damping property can be further improved without adversely affecting the strength and toughness.

It is ideal to increase the (100) texture at a portion closer to the steel sheet surface, but it is actually difficult. A condition that is actually effective in improving the vibration damping properties of the steel sheet is that the (200) plane intensity ratio by X-ray diffraction measured at a portion having a thickness of 1/8 as a representative value is 1.5 or more. If the (200) plane strength ratio at the site is 1.5 or more, the texture in the surface layer portion from immediately below the surface layer to about 1/6 of the plate thickness has a favorable distribution for improving vibration damping properties.
0) Clear improvement in vibration damping can be expected as compared with the case where the surface strength ratio is less than 1.5.

On the other hand, since the contribution of the internal texture to the vibration damping property is smaller than that of the surface, it is necessary to develop a stronger texture in order to exhibit the effect of improving the vibration damping property. Based on this, it was measured at the center of the thickness (2
00) The surface intensity ratio needs to be 3.0 or more. When the (200) plane intensity ratio at the site is less than 3.0, the superior difference from the case where the texture is not developed is not clear.

The above is the organizational requirement of the present invention for ensuring both vibration damping and toughness.

If the above-mentioned organizational requirements of the present invention are satisfied, it is possible to achieve both good vibration damping properties and good materials regardless of the achievement means. Means for achieving the invention have also been invented. Hereinafter, a manufacturing method for achieving the organizational requirements of the present invention will be described in detail.

The essential point of the production means of the present invention for satisfying the structural requirements of the present invention is to change the residual dislocation density in the surface layer and the inside by modifying the rolling, and to change the recrystallization behavior in the subsequent heat treatment to obtain the surface layer. The purpose is to form different textures and crystal grain sizes between the part and the inside. Specifically, it is roughly classified into the following two methods.

That is, the first method is as follows.
When heating to 0 ° C or more and 1300 ° C or less, and when performing billet thickness or rough rolling, the cumulative rolling reduction in the austenite region of 950 ° C or more is 80% or less, and 10% of the billet thickness after performing rough rolling. It is necessary to start cooling at a cooling rate of 2 to 40 ° C./s from a temperature higher than the _{Ar 3} transformation point to a surface layer region corresponding to ３５35%, stop cooling below the _{Ar 3} transformation point, and recover heat. In the process of passing more than once, after the finish rolling with a cumulative rolling reduction of 10 to 80% is completed until the reheating after the last cooling is completed, the heating temperature is further increased to 650 ° C. to the A _C1 transformation point. Tempering or annealing process "
The second method is as follows: "The slab is heated to 1000 ° C. or more and 1300 ° C. or less, and firstly, rolling is completed at 900 ° C. or more, and rough rolling is performed at a cumulative rolling reduction of 10% to 80%. Is below the _Ar3 transformation point and the end temperature is above 600 ° C,
After performing finish rolling with a rolling reduction of 20% or less per pass and a cumulative rolling reduction of 30% to 80%, a heating temperature of 650 ° C. to a tempering or annealing treatment at the A _C1 transformation point is applied. is there. The reasons for the limitations are described below for each method.

First, the first method will be described. First
The method of, in order to impart a different rolling effect to the surface layer and the inside, once cooled the surface layer to a low temperature by water cooling,
By further rolling the ferrite region to the two-phase region structure in the process of recuperating by internal sensible heat, more dislocations are introduced into the surface layer portion.
When heating to 0 ° C or more and 1300 ° C or less, and when performing billet thickness or rough rolling, the cumulative rolling reduction in the austenite region of 950 ° C or more is 80% or less, and 10% of the billet thickness after performing rough rolling. It is necessary to start cooling at a cooling rate of 2 to 40 ° C./s from a temperature higher than the _{Ar 3} transformation point to a surface layer region corresponding to ３５35%, stop cooling below the _{Ar 3} transformation point, and recover heat. In the process of passing more than once, after the finish rolling with a cumulative rolling reduction of 10 to 80% is completed until the reheating after the last cooling is completed, the heating temperature is further increased to 650 ° C. to the A _C1 transformation point. Perform the tempering or annealing treatment "to achieve the structural requirements of the present invention.

First, the steel slab is reheated to the austenite region.
0 ° C. or lower is preferred. That is, if the temperature is less than 1000 ° C., not only the surface layer but also the inside is subjected to two-phase region processing due to the temperature drop during rolling, so that it is difficult to form different structures and textures between the surface layer and the inside. In addition, there is a problem that the anisotropy of the steel material increases. On the other hand, when the temperature exceeds 1300 ° C., the grain size of the heated austenite becomes extremely coarse, so that the grain size cannot be reduced by subsequent rolling, and the grain size is reduced to such an extent that the toughness is not adversely affected from the surface layer to the center of the sheet thickness. In some cases, it is impossible to ensure toughness. Therefore, in the present invention, the heating temperature of the steel slab is limited to 1000 ° C. or higher to 1300 ° C.

After the slab is reheated to the austenite region under the above conditions, and directly or if necessary, rolled in the austenite region, the thickness of the slab at that stage is reduced to 1%.
The surface region corresponding to 0% to 35% starts to be cooled at a cooling rate of 2 to 40 ° C./s from a temperature not lower than the _Ar3 transformation point.
_{In the} process of stopping cooling at less than the _r3 transformation point and reheating at least once, finish rolling with a cumulative reduction ratio of 10 to 80% is performed until reheating after the last cooling is completed. .

Only the surface layer has a ferrite region to ferrite /
A surface layer for processing during recuperation in the austenitic two-phase region
Part is quenched by means such as water cooling.
10% to 35% of slab thickness or steel thickness at the time of rolling
The corresponding surface layer area is A _r3Cool below the transformation point
At the same time, a temperature difference is created between the surface layer and the inside,
This corresponds to 10 to 35% of the thickness of the steel material before water cooling.
The cooling rate of each surface layer area must be 2 ° C / s or more.
There is. This means that if the cooling rate is less than 2 ° C / s,
No remarkable temperature difference between the inside and the surface layer
This is because it is difficult to process in the process. High cooling rate
Although it is preferable to have a rapid cooling,
In addition to saturating the fruits, unnecessary quenching is the shape of the steel plate.
Because it is not preferable for maintenance, the upper limit is 40 ° C / s.
I do.

The above cooling is performed by A_r3Open from above the transformation point
Start. This is because the cooling start temperature is A _r3Lower than the transformation point
The interior is inevitably subjected to two-phase rolling,
The difference between the organization and texture of the surface layer and the interior
The surface layer is cooled by cooling from single-phase austenite.
This is to make the tissue uniform.

As will be described later, the processing in the recuperation process is 1
May be repeated twice or more times, but the cumulative draft is 10 to 80% until the reheating after the last cooling is completed.
Finish rolling. By the rolling, the ferrite structure formed in the cooling-reheating process is processed to increase the dislocation density in the ferrite matrix.
%, The dislocation density finally remaining is not sufficient, and the structure cannot be controlled by heat treatment. On the other hand, if the cumulative rolling reduction of the finish rolling is more than 80%, it recrystallizes into a fine-grained structure in the heat treatment stage, and the surface layer may have a ferrite structure having a particle size appropriate for improving the vibration damping property. It will be difficult.

The above-described processing steps during cooling to less than the _{Ar 3} transformation point and reheating may be performed once, but the effect is superimposed by repeating a plurality of times, so that a desired structure can be obtained even if the processing is repeated twice or more. It is possible. In this case, even if the maximum temperature or the minimum temperature in each recuperation stage is arbitrary, ultrafine granulation is performed according to the temperature conditions of the present invention. However, it is preferable to set the upper limit of the recuperation temperature in the middle to be equal to or lower than the A _C3 transformation point in order to ensure the processing effect.

When the difference between the thickness of the slab and the thickness of the finished plate is large, rough rolling may be performed in the austenite single-phase region if necessary. Since it is not preferable to make the difference in texture and crystal grain size between the surface layer and the inside afterwards, the rolling is completed in the austenite recrystallization region or the unrecrystallized region is rolled. It is necessary to take care that the amount of processing does not increase even if it is performed. For this reason, in the present invention, the conditions for performing the rough rolling are as follows: "The cumulative rolling reduction in the austenite region of 950 ° C. or more is 80%. Below.

Regarding the cooling conditions after the completion of hot rolling, the structure after rolling becomes a ferrite-based structure regardless of the cooling conditions in the composition of the present damping alloy, and has a particularly great effect on the formation of the structure after heat treatment. Therefore, it may be allowed to cool or accelerate cooling. However, it is not preferable that the structure of the surface layer recrystallizes and grows during cooling after rolling, and thus extreme slow cooling is not preferable. Specifically, slow cooling in which the average cooling rate from the end of rolling to 200 ° C. is less than 5 ° C./min should be avoided.

After the above rolling, a tempering or annealing treatment at a heating temperature of 650 ° C. to the A _C1 transformation point is finally performed to form the structural requirements of the present invention. If the heating temperature is lower than 650 ° C., the progress of recrystallization is insufficient even in the surface portion having a high dislocation density, and the desired ferrite grain size and texture cannot be obtained. On the other hand, when the temperature exceeds the A _C1 transformation point, austenitization starts, and this austenite phase is not preferable because it forms agglomerates of martensite or carbide that adversely affect vibration damping properties and toughness during tempering or annealing. Therefore, the heating temperature for tempering or annealing needs to be limited to 650 ° C. to the AC ₁ transformation point.

The holding time of the heat treatment does not have such a large effect as the temperature, so it may be selected according to the desired characteristics. However, if the holding time is less than 1 minute, the uniformity of the temperature distribution tends to be insufficient. Therefore, when the time is longer than 48 hours, a change in the chemical composition of the surface or rough skin may be concerned. Therefore, it is preferable to select a time within the range of 1 minute to 48 hours. Regarding the cooling condition, since the formation of the structure and the texture during the heating and holding is completed, there is no particularly significant effect except for extreme quenching. Rapid cooling such as water cooling should be avoided because it causes distortion due to non-uniform cooling and causes deterioration of damping performance.

Next, "The slab was heated to 1000 ° C. or higher,
C. or lower, and first perform rough rolling at a cumulative rolling reduction of 10% to 80% at which rolling is completed at 900 ° C. or higher, and subsequently, when the starting temperature is lower than the _{Ar 3} transformation point and the ending temperature is 600 ° C. or higher, at a reduction ratio per one pass is 20% or less, and after the cumulative rolling reduction was 30% to 80% of the finish rolling, further heating temperature subjected to tempering or annealing treatment of 650 ° C. to a _C1 transformation point "that A characteristic second method will be described.

When the heating temperature of the billet is 1000 ° C. or more,
The reason for limiting the temperature to 0 ° C. or lower is exactly the same as the reason in the first method.

After the steel slab is heated in the temperature range, before the rolling in the two-phase zone, in order to adjust the sheet thickness and to make the austenite grain size constant, the cumulative reduction ratio is 10% to 80%. Rolling is completed at a temperature of 900 ° C. or more. This is because it is not preferable to control the structure of the ferrite structure by forming the austenite work texture remarkably over the entire thickness by the rolling, so that the rolling is completed in the austenite recrystallization region or the unrecrystallized region is rolled. This is because it is necessary to take care not to increase the processing amount. That is, if the rolling end temperature is lower than 900 ° C., the rolling reduction in the non-recrystallized region necessarily increases, which is not preferable. The rolling reduction of the rolling is 1
If it is less than 0%, there is no effect in reducing the austenite grain size, and if it is more than 80%, the development of the austenite texture cannot be ignored, which is not preferable. Therefore, the rolling reduction in the austenitic region where the rolling is completed at 900 ° C. or more is limited to 10% to 80%.

Following the austenitic rolling, the starting temperature is lower than the _{Ar 3} transformation point and the ending temperature is higher than 600 ° C.
Finish rolling is performed in which the rolling reduction per pass is 20% or less and the cumulative rolling reduction is 30 to 80%. That is, by performing rolling under the above conditions, it is possible to form a different ferrite grain size and texture between the surface layer and the inside as shown in claim 1 during recrystallization and grain growth in the subsequent heat treatment. It becomes possible. For recrystallization and grain growth by heat treatment, it is necessary to introduce processing strain into the ferrite, and therefore, the rolling start temperature must be equal to or lower than the _Ar3 transformation point. However, if the ending temperature is lower than 600 ° C., the rolling reaction force becomes excessively large and the steel sheet shape may be deteriorated. The cumulative rolling reduction is set to a range of 30 to 80% as long as the effect of the processing is secure and the grain size is not extremely reduced by the heat treatment. The rolling reduction also needs to be limited to 20% or less.

The effects of the cooling, tempering and annealing after rolling in the second method on the structure and the material are exactly the same as those in the first method, so that the limiting contents are exactly the same.

The above is a description of the requirements relating to the structure and the manufacturing method in the present invention. Even if the requirements for the structure of the present invention are satisfied, individual requirements for achieving good vibration damping properties, strength and toughness are obtained. The chemical components also need to be limited for the following reasons.

C has a different degree of adverse effect on toughness and damping properties depending on whether it is in a solid solution state or a precipitate, but in any state, the damping property is greatly deteriorated. 0.03% upper limit as acceptable amount
And

Si is an element required as a deoxidizing agent, and must be added in an amount of 0.01% or more in order not to cause defects due to insufficient deoxidation. In addition to the effect as a deoxidizing agent, Si is also effective for increasing the strength and coarsening as a ferrite stabilizing element. However, even if added in excess of 3.5%, the above effect is saturated. The upper limit is set to 3.5% since the vibration damping property is deteriorated due to the coarse oxide and the toughness is significantly deteriorated.

Mn is added in an amount of 0.3% or more in order to secure strength. However, if added in excess, the transformation point is lowered, so that coarsening becomes difficult and the vibration damping property is deteriorated. Since the weldability is also reduced, an allowable range is determined from an experiment, and the upper limit is set to 3.0%. P and S, as impurity elements, segregate and become inclusions, which have a remarkable adverse effect on vibration damping properties and toughness. Therefore, it is preferable to reduce P and S as much as possible. Is 0.0
10% or less.

Cr is a ferrite stabilizing element, an element that enhances the vibration damping properties through coarsening of crystal grains and by solid solution Cr, and is an important element in a ferromagnetic damping alloy. In order to exert the effect, it is necessary to add 0.01% or more. As the Cr content is increased, the vibration damping property is improved. However, if the addition exceeds 5.0%, the vibration damping property improving effect is saturated, but the toughness is deteriorated. Therefore, in the present invention, the upper limit is 5.0%. I do.

Although Al is important as a deoxidizing agent, it is also an important element for improving vibration damping. In order to exert the effect, 0.002% or more is necessary. However, if added excessively, inclusions such as Al ₂ O ₃ and AlN and precipitates become coarse and the toughness is reduced, so the upper limit is 3.5. %.

N, like C, is an element that has an adverse effect on the vibration damping properties both in a solid solution state and in a precipitated state. Therefore, it is preferable to reduce N as much as possible, but if Al is added within the scope of the present invention, Addition of up to 0.01% is permissible because it does not adversely affect the damping properties and toughness.

The reasons for limiting the basic components of the steel material according to the present invention have been described above. In the present invention, Cu, Ni, Mo, W, Nb, T
One, two or more of a, V, Ti, Zr, and B can be contained.

Cu is an element capable of simultaneously improving the strength and toughness of the base material.
The above is necessary. Conversely, if the content exceeds 1.5%, there is a problem in hot workability, so the content is limited to the range of 0.05 to 1.5%.

Ni is an element that can simultaneously improve the strength and toughness of the base material, like Cu, and is an element particularly effective in improving the toughness. However, it is necessary to contain 0.05% or more in order to exert the effect. There is. When the content is increased, the strength and toughness are improved. However, if the content exceeds 2.0%, the effect is saturated, but the vibration damping property and the weldability are deteriorated.
0%.

Mo is an element effective for improving the strength of the base material, but is required to be 0.05% or more in order to produce a clear effect. Since the toughness and the weldability tend to be deteriorated together with the properties, they are respectively set in the range of 0.05 to 2.0%.

Similarly to Mo, W is effective in increasing the strength of the base material by solid solution strengthening and precipitation strengthening, but is required to be 0.05% or more in order to exhibit the effect. On the other hand, if the content exceeds 2.0%, the damping property and the toughness deteriorate significantly, so the upper limit is made 2.0%.

Nb is an element effective for improving strength and toughness by forming Nb (C, N). However, when Nb is excessively contained, both vibration damping property and toughness are deteriorated due to precipitates. Therefore, the range in which the effect can be exhibited without deteriorating the vibration damping property and toughness is limited to the range of 0.005 to 0.20%.

Ta is also an element effective for improving the strength and toughness, but it is necessary to contain 0.005% or more in order to exhibit the effect. On the other hand, if it exceeds 0.50%, precipitation embrittlement, coarse precipitates, and inclusions cause deterioration of damping properties and toughness, so the upper limit is made 0.50%.

V is also an element effective for improving the strength by forming VN. However, if it is contained excessively, the precipitates deteriorate the vibration damping property and toughness. Therefore, the range in which the effect can be exerted without causing significant deterioration in toughness is limited to the range of 0.005 to 0.50%.

Ti contributes to the improvement of the base metal strength by precipitation strengthening, and is also an element effective in reducing the austenite grain size by formation of TiN, and is also effective in improving the toughness. For this purpose, a content of 0.002% or more is required. On the other hand, if it exceeds 0.02%,
The upper limit is made 0.02% because coarse precipitates and inclusions are formed to deteriorate the vibration damping property, toughness and ductility.

Zr is also an element forming nitride, and Ti
Has the same effect as described above, but in order to exhibit the effect, the content of 0.002% or more is necessary. On the other hand, 0.10
%, Coarse precipitates and inclusions are formed similarly to Ti to deteriorate the vibration damping property and toughness.
It is limited to the range of 0.10%.

B is an element that is effective for improving toughness and damping property by solid solution N fixation, and for improving strength and toughness by improving hardenability because B is surely linked to N in a trace amount. Is required to be 0.0003% or more. On the other hand, 0.00
If it is contained in excess of more than 30%, BN becomes coarse, adversely affecting vibration damping and toughness. Further, since the weldability is also deteriorated, the upper limit is made 0.0030%.

Further, in order to improve ductility and joint toughness, one or more of Ca, Mg, and REM can be contained as necessary.

Each of Ca, Mg, and REM is effective in suppressing the elongation of sulfide during hot rolling and improving ductility.
It also works effectively to improve the joint toughness by making the oxide finer.
The lower limit contents for exhibiting the effect are respectively Ca
Is 0.001%, Mg is 0.0002%, and REM is 0.001%. On the other hand, if it is contained excessively, sulfides and oxides are coarsened to cause deterioration of damping property and ductility. Therefore, the upper limits are 0.05% for Ca and 0.01% for Mg.
% And REM are 0.05%.

[0070]

The above has been a description of the requirements of the present invention. The effects of the present invention will be further shown based on examples.

Using test steels having the chemical compositions shown in Table 1, steel sheets were manufactured under the manufacturing conditions shown in Tables 2 and 3. Tables 2 and 3 also show the structural requirements and mechanical properties (tensile properties, 2 mmV notch Charpy impact properties, vibration damping properties) of the manufactured steel sheet related to the present invention. Table 2 shows the results of the present invention manufactured by the manufacturing method of the present invention described in claim 5 and comparative examples, and Table 3 shows the examples of the present invention manufactured by the manufacturing method of the present invention described in claim 6. It is the result which showed and the comparative example.

The tensile properties were measured by taking a round bar tensile test piece from the center of the sheet thickness in the direction (L direction) parallel to the rolling direction. The toughness was evaluated by the fracture surface transition temperature (vTrs) in the 2 mm V notch Charpy impact test, and the test piece was taken from the center in the L-direction thickness as in the case of the tensile properties. The damping property was determined by measuring the loss coefficient (η) by a mechanical impedance method using a test piece having an original thickness × 40 mm width × 400 mm length, which was sampled so that the longitudinal direction of the test piece was parallel to the rolling direction. I asked.

In the present invention, the index and measuring method of the (100) texture which greatly affects the vibration damping properties are as follows.

Usually, the texture is measured by X-ray diffraction. For example, for a detailed measurement of the (100) texture, the sample is biaxially rotated by a pole figure apparatus, and the (200) reflection (ferrite is crystal The texture is determined by measuring the intensity (because there is no (100) reflection due to the extinction law due to the structure). In this case, the peak value of the intensity near the center of the (100) pole figure created as a result of the analysis gives the diffraction intensity ratio used as an index in the present invention. However, since pole figure creation requires a long time for data collection and calculation, as a simple method, the (200) reflection intensity measured by a normal wide-angle X-ray diffractometer is used to strengthen or control a specific crystal orientation. It is also possible to use a diffraction intensity ratio of several times that of a material having a completely random crystal orientation.

Further, the measurement of the ferrite particle size is based on JIS G
In accordance with No. 0552 "Testing method of ferrite crystal grain size of steel", an appropriate optical microstructure photograph of 50 to 500 times was performed by a cutting method.

Test Nos. In Tables 2 and 3 A1 to A1
6 is a steel sheet manufactured by the manufacturing method of the present invention using steel numbers 1 to 12 having the chemical composition of the present invention, which satisfies the structural requirements of the present invention, and all have good vibration damping properties and It is clear that strength and toughness are achieved at the same time.

On the other hand, from the results of Tables 2 and 3, test Nos. The steel sheets of Nos. B1 to B13 are the test Nos. Manufactured by the present invention. It is clear that one or both of the damping property and the toughness are significantly inferior to the steel sheets of A1 to A16.

Test No. B1 to B5 are comparative examples in which one or both of the vibration damping property and the toughness are inferior because the chemical composition does not satisfy the present invention, although they are produced by the method of the present invention.

That is, the test No. In B1, since C, which has the most adverse effect on the damping property, is excessive, both the damping property and the toughness are significantly inferior even though the organizational requirements of the present invention are satisfied.

Test No. In B2, since Si is excessive, the deterioration of toughness is remarkable, and no improvement in damping properties is achieved.

Test No. B3, like C, has excessive N, which deteriorates the vibration damping property, so that the vibration damping property is greatly deteriorated. Poor toughness.

Test No. B4 has relatively good toughness due to excessive addition of Ni, but has poor vibration damping properties.

Test No. B5 is inferior in both toughness and vibration damping properties due to excessive Mo.

Test No. B6 to B8 are examples in which the chemical composition satisfies the present invention but do not satisfy the requirements of the present invention with respect to the production method of claim 1.

That is, the test No. B6 does not include a cooling / reheating step of the surface layer before the finish rolling, so that there is no difference in texture and texture between the surface layer and the inside, which is a feature of the present invention. Vibration damping properties and toughness are slightly inferior to those of the examples of the present invention satisfying the structural requirements of the present invention.

Test No. B7 has an excessively large rolling reduction in the final finish rolling after the cooling and reheating step, so that the surface layer,
The inside is finer than the required ferrite grain size, resulting in good toughness but poor vibration damping.

Test No. In B8, since the tempering temperature applied after rolling is too high and the temperature is in the two-phase region, island-like martensite is generated, and both toughness and vibration damping properties are significantly deteriorated.

Test No. B9 and B10 are comparative examples in which one or both of the vibration damping property and the toughness are inferior because the chemical composition does not satisfy the present invention.

That is, the test No. B9 is the test No.
As in B1, because C is excessive, the structural requirements of the present invention are satisfied, but the vibration damping properties and toughness are significantly poor.

Test No. Test No. B10 was also tested. As in B2, the excess of Si causes significant deterioration in toughness and poor vibration damping.

Test No. B11 to B13 are examples in which the chemical composition satisfies the present invention but do not satisfy the requirements of the present invention with respect to the production method of claim 2.

That is, the test No. In B11, since the cumulative rolling reduction of the finish rolling is excessive, the rolling reduction of each pass is 2%.
Even if the requirement of the present invention of 0% or less is satisfied, since the finally obtained ferrite particle size is excessively fine in both the surface layer and the inside, the improvement in vibration damping properties is not sufficient.

Test No. B12 is the test No. Contrary to B11, the cumulative rolling reduction satisfies the requirements of the present invention,
Since a rolling reduction in which the rolling reduction per pass exceeds 20% is included, the ferrite grain size and texture of the surface layer portion do not satisfy the present invention, and the improvement of the vibration damping property is not sufficient.

Test No. B13 is because the recrystallization of the processed structure does not sufficiently proceed because the tempering temperature is too low.
Again, the ferrite grain size and texture of the surface layer do not satisfy the present invention, and the vibration damping properties are poor.

From the above examples, according to the present invention, it is possible to further improve the vibration damping property without deteriorating the toughness, and as a result, the vibration damping property and the strength / toughness are compatible. It is clear that it is possible to produce damping alloys with favorable properties as structural materials.

[0096]

[Table 1]

[0097]

[Table 2]

[0098]

[Table 3]

[0099]

According to the present invention, it becomes possible to secure not only the vibration damping property but also the strength, toughness, etc. necessary for the structural material.
As a result, it is possible to provide a damping alloy that can be used as a structural material for ships, bridges, industrial machines, construction, and the like, and the industrial effect is extremely large.

 ────────────────────────────────────────────────── ─── Continuing on the front page F term (reference) 4K032 AA01 AA04 AA08 AA11 AA12 AA14 AA15 AA16 AA17 AA19 AA20 AA21 AA22 AA23 AA24 AA27 AA29 AA31 AA32 AA33 AA35 AA36 AA37 AA39 AA01 CA02 CA03 CF03

Claims (6)

[Claims] An average ferrite grain size from the front surface to the back surface of each of the steel plates in the thickness direction from the surface to 1/6 of the thickness is 70 μm.
Above, less than 150 μm, the average ferrite grain size inside the steel plate other than the region is 20 μm or more, less than 50 μm,
The ferrite phase has a (200) plane intensity ratio of 1.5 or more measured by X-ray diffraction measured at a thickness of 1/8 from the surface in the thickness direction, and the ferrite measured by X-ray diffraction measured at the center of the thickness. A high toughness vibration damping alloy, wherein the (200) plane strength ratio of the phase is 3.0 or more. 2. In% by weight, C: 0.03% or less, Si: 0.01 to 3.5%, Mn: 0.3 to 3.0%, P: 0.020% or less, S: 0 0.010% or less, Cr: 0.01 to 5.0%, Al: 0.002 to 3.5%, N: 0.01% or less, with the balance being Fe and unavoidable impurities. The high toughness damping alloy according to claim 1. 3. Cu: 0.05-1.5%, Ni: 0.05-2.0%, Mo: 0.05-2.0%, W: 0.05-2. 0%, Nb: 0.005 to 0.2%, Ta: 0.005 to 0.5%, V: 0.005 to 0.5%, Ti: 0.002 to 0.02%, Zr: 0 The high toughness vibration damping alloy according to claim 2, further comprising one or more of 0.002 to 0.10% and B: 0.0003 to 0.003%. 4. One or more of Ca: 0.001 to 0.05%, Mg: 0.0002 to 0.01%, and REM: 0.001 to 0.05% by weight. The high toughness vibration damping alloy according to claim 2, wherein the alloy is contained. 5. The following steps are started immediately after heating the steel slab to 1000 ° C. or higher and 1300 ° C. or lower, or after performing rough rolling with a cumulative rolling reduction of 80% or lower in an austenite region of 950 ° C. or higher. 10% to 3% of the thickness of the slab immediately before
It is necessary to start cooling at a cooling rate of 2 to 40 ° C./s from the temperature above the _Ar3 transformation point to the surface layer region corresponding to 5%, and stop the cooling below the _Ar3 transformation point to regain heat. In the process of passing, after the finish rolling with an accumulated draft of 10 to 80% is completed until the reheating after the last cooling is completed, the heating temperature is further increased to 650 ° C. to temper the A _C1 transformation point. Or performing an annealing treatment.
5. The method for producing a high toughness vibration damping alloy according to any one of 4. 6. The steel slab is heated to 1000 ° C. or higher and 1300 ° C. or lower, and after rolling at 900 ° C. or higher, rough rolling is performed with a cumulative rolling reduction of 10% to 80%, and the starting temperature is _{Ar 3.}
At the transformation point or lower, the end temperature is 600 ° C. or higher, the rolling reduction per pass is 20% or less, and the cumulative rolling reduction is 30 to 80.
% Finish rolling, and thereafter, a heating temperature of 65%
The method for producing a high toughness vibration damping alloy according to any one of claims 1 to 4, wherein a tempering or annealing treatment at 0 ° C to A _C1 transformation point is performed.